Shunt-contact for electric switches.



W. M. SCOTT. SHUNT CONTACT FOR ELECTRIC SWITCHES.

APPLIOATION FILED MAR. 26, 1907.

91 4,677, Patented Mar. 9, 1909.

mawauh a qbihwaaey r I 3% Ma W I it lmf rwli- '10 all whom it may concern: I

Be it known that l, WJLLLAM M. Scorr, a citizen of the Umted States, residing at cation:

WILLIAM MfSCO TT, OF PHILADELPHIA, PENNSYLVANIA.

I SHUNT-CONTACT FOR ELECTRIC SWITCHES.

v Specification of Letters Patent.

Patented March 9, 1909.

Application filed March 26, 1907. Serial No. 364,720.

Philadelphia, in the county of Philadelphia and State of Pennsylvania, have invented a new and useful Shunt-Contact for Electric Switches, of which the following is a specifi- My invention relatesto electric switches or circuit breakers and more particularly to 1P wthe means for preventing arcing at the switch or circuit breaker contacts.

7 It has heretofore been the practice to sup plement the main switch with a shunt switch or shunt path which opens after the main switch contactsfso that the arcing is confined to the shunt contacts, the shunt con tacts being generally of carbon. It has also been the practice to have a second shunt path, intermediate between the main switch and the carbon switch to cause a more perfect graduation in the introduction of resistance into the circuit during the circuit breaking operation. Those intermediate shunt contacts, were ofmetal, the o eration being the rupture of the circuit at t is main contacts, later at the metallic shunt contacts, and finally, at the carbon contacts.

It is the object of my invention to simplify switch construction inthis regard and to entirely eliminate the intermediate metallic or other shunt contactsyan'd to employ only one shunt path. To this end I employ as shunt contactspieces or blocks of material consisting of a mixture of refractory 'material with comminuted or suitably fmel divided non-refractory conducting materia For the. refractory material carbon, or

other conductor or non-conductor, may be employed and for the non-refractory conducting material maybe employed finely divided metal as copper, aluminum, or any other I a suitable metal or material, 'of either high or low s ecific resistance. The material is prepared by thoroughly mixing finely'divided carbon, either in the amorphous or graphitic state, (or other refractory material) and finely divided metal such as aluminum, copv I per, etc. (or other suitable conducting nonrefractory material) with a suitable binding material and then subjecting the mixture to l pressure in suitable molds, and baking to a greater or less extent, though baking mayprobabl in some instances, be dispensed 55 with. y using blocks of such mixtures for the shunt contacts the intermediate metallic shunt contact may be entirel dispensed with and the circuit successfully ruptured without damage to the main contacts.

vteferring to the accompanying drawing, which is a side elevation of an automatic circuit breaker, 1 represents a base of any suitable insulating material, such as slate or marble, upon which are secured terminal blocks 2 and 3, preferably of copper, which are adapted to be engaged and brid ed by .the laminated bridging member 4, W 'ch 18 mechanically supported upon but insulated from the arm-5 pivoted at G in the bracket or housing 7. The arm 5 is controlled and operated by the operator s lever 8 pivoted at 9 in the bracket 7. The lever 8 as an inwardly extending portion 10 which is pivoted at 11 to the link 12, which latter is, in turn, pivoted at 13 to the arm 5. The member 10 and the link 12 constitute a tog le which serves to cramp the bridging mom or 4 into firm engagement with the terminal blocks 2 and 3, as well understood in this art. The operators'lever 8 has pivoted upon it at 14 a small roller 15 adapted to be enga ed and held by the latch 1.5 pivoted to the bracket silient member 24 supported by and insulated from the arm 5, and in electrical communication with the lower terminal block 3. The shunt contact pieces 21 and 23 consist of -any of the mixtures hereinbelore described.

When the operatorfs'lcver 8 is released from the latch 15, the toggle 10, 12 collapses and the arm 5 rotates upon its pivot 6 carrying the laminated bridging member 4 away from and out of contact with the terminal blocks 2 and 3. The shunt contact pieces 21 and 23 remain in contact,-however, an interval of time after the laminated bridging member has separated from the contact blocks 2and 3 and the circuit remains com-- pleted throu h these pieces 21 and 23, for" that interva of time. Since these shunt contact pieces consist of the'mixtures heretofore described, the current finds a path through them which is not so highly resistant "as if simply refractory conducting material, as carbon, were employed. It ollows, therefore, that the intermediate metallic shunt contact heretofore commonly employed may be entirel dispensed with for the resistance of the at through the pieces 23 and 21 is-low.

enoug to absolutely prevent an arcing or sparking between the bridge 4 an the terminals 2 and 3. And yet the properties of the shunt contact pieces 21 and 23 are such, thatupon further opening movement of the parts,

they separate and the final arcing takes lace between them without dama ing saids unt contact pieces even thou h t ere is non-re-j fractory conducting meta present.

By emplo in the mixtures herein describedfor t e s unt contact pieces, the in-' termediate shunt contact pieces may be dispensed with, as stated, and yet all the properties of a simple refractory metallic shunt piece retained for the final breaking breaker involving a laminated bridging memher, it is. to be understood that the same may be employed also with switches or circuit breakers employing other types of contacts for the main switch, as, for example, the knife-blade forms.

What I claim is:

' 1. In an electrical switch, a shunt contact consist of a mixture of conducting material an 'finely divided material of higher conductivity. I

-2. In an electrical switch, a, shunt contact consisting of a mixture of carbon and finely divided metal.

In testimony whereof I have hereunto aflixed my signature in the presence of the two subscribing Witnesses.

- WILLIAM M. SCOTT.

Witnesses:

DANLfWEBs'rER, Jr., ANNA E. STEINBOOK. 

